Hi Pamela,
You are exactly correct. Fantasyland is a part of the Magic Kingdom Park. As long as you have admission to the Magic Kingdom Park, once you are inside, there is no additional ticket required for Fantasyland.
While you are there, be sure to check out
New Fantasyland. This section of the park just opened. It includes the amazing Enchanted Tales with Belle attraction, where Belle and Lumiere host a wonderful retelling of the Beauty and the Beast Story. If you can, try to grab lunch at Be Our Guest Restaurant, a fabulous restaurant themed as Beast's Castle. Over in the Storybook Circus section, you will find two spinning Dumbo the Flying Elephant attractions and a great child-friendly roller coaster, The Barnstormer.
Have a wonderful time at the Magic Kingdom Park and exploring Fantasyland, Pamela. Please do not hesitate to ask if you have any further questions!